1. Field of the Invention
This invention relates to a halogen-free flame retardant crosslinkable resin composition, as well as a cross-linked insulation wire and a cable using the resin composition.
2. Description of the Related Art
An electric wire and a cable applied to a railway vehicle, a motor car, an apparatus and the like are required to have high abrasion resistance, high flame retardancy, excellent low temperature characteristic and the like as needed.
For the purpose of achieving high abrasion resistance, a use of a polymer such as HDPE having high crystallinity as a base polymer constituting an insulating layer is known.
The polymer having high crystallinity, however, has low filler receptivity, thus it is necessary to reduce the additive amount (content) of the filler. Consequently, a halogen based flame retardant or a phosphorus based flame retardant such as red phosphorus that has an effect on flame retardancy by the addition of small amounts is necessarily used.
The halogen based flame retardant, however, generates a halogen gas at the time of combustion, thus the use thereof lacks consideration to the environmental problem to which concern is rising throughout the world. In addition, the phosphorus based flame retardant such as red phosphorus also generates phosgene at the time of combustion and produces phosphoric acid at the time of disposal so as to problematically contaminate underground water vein.
Then, a flame retardant resin composition to which a metal hydroxide that is a halogen-free based flame retardant is added is known (for example, refer to JP-A-2002-60557 and JP-A-2004-156026).
The metal hydroxide does not cause the above-mentioned problem in comparison with the halogen based flame retardant or the phosphorus based flame retardant, but is needed to be filled with high density, thus there is a problem that mechanical characteristic including abrasion resistance and low temperature characteristic are reduced.